I was able to get to ~500 day streak in french on duolingo. there was certainly a few freebie days in there for free. I thought I was doing great.
Then I bought a bunch of french books for my daughter and learnt I knew nothing.
Then I bought a bunch of french books for my daughter and learnt I knew nothing.
Was it really the case that you didn't know anything in the books? That would be very surprising. At the very least you'd expect to recognize vocabulary you've encountered before, even if the sentences weren't familiar. I'd have thought after 500 * 15 minutes you'd be able to figure some things out.
As it is though, even if the books were completely unfamiliar, I don't really know how you'd measure or test that Duolingo had had no impact on you. Obviously if a book has vocabulary in it that you've not encountered on Duolingo then you're not going to know what it means, but how could you know that you aren't picking up new things faster because you've worked through Duolingo first?
My experience of it has been very different. I work through Duolingo courses for languages I build software in. I've not spent anywhere close to 500 days on any language yet, but I've found I am able to work with languages better having done a few months of Duolingo courses. When I've been working on German and Spanish websites I've actually understood much more of the text than I could with websites I haven't learnt any of. I mean, I couldn't drop in to Madrid and have a chat with someone, but it definitely has made a difference.
Honestly, probably not fluent in any language except python. I probably need to put significantly more effort into learning the language than I was doing.
I hate the gendered nature of french. I love quebecois over the french academy crap.
I guess I'm not an ideal student by any means.